Nothing on Earth sounds better to a gearhead than an uncorked open-header engine. It's the sound of power, the thumping racket that makes you tingle all over. Unfortunately, if you want to drive on the street, that octane-fueled mechanical music needs to be knocked down a few decibels to satisfy the local constabulary. But silencing the beast under your hood doesn't have to put serious hurt on the power getting to the wheels. By selecting the right exhaust system, you can have the best of both worlds.
Our '70 Fairlane is offbeat-cool, but thinking outside of the box has a price. That price is that it's hard, or impossible, to find vehicle-specific performance parts. Everybody makes stuff for 69 Camaros, but when we looked foran off-the-shelf exhaust system for our Fairlane, we were greeted by the sound of crickets. This meant going custom. The folks at MagnaFlow had just the right parts in stock to build a system that would sound great without robbing power from the 552hp small-block residing under the hood.
MagnaFlow doesn't make a kit...
MagnaFlow doesn't make a kit for a '70 Fairlane, so we had to go custom. MagnaFlow measured, marked, cut, test-fit, trimmed, and tack welded the pieces together. Once everything was mocked, all the parts were TIG welded. More than enough material was included in MagnaFlow's Hot Rod kit.
The decision was what size and type of system to install. Should it be 2.5- or 3-inch? Should it run all the way back or end after the mufflers? Is an X-pipe worth the extra coin? MagnaFlow does this for a living, and we decided to pick their brains to see where we would get the most performance benefit.
Regarding pipe diameter, Richard Waitas, engineering director for MagnaFlow, told us: "In choosing between a 3- and 2.5-inch exhaust for a dual-role street/strip car, considerations in sizing are not purely based on peak power. In a race application, it is easy to build an exhaust that will permit max cfm flow at peak horsepower rpm. In an all-out strip car with a high-stall converter and airflow ranged toward high rpm, the larger-diameter system will definitely shine, but this is only the case in an application where the powertrain is designed for peak performance. Determining where your application fits most should sway you from smaller to larger. In a more street or street/strip application, consideration for the rest of the curve should be made, as power delivery 'feel' will be substantially different. This feel is often the difference in torque or midrange horsepower. Some of this midrange power and low-rpm torque is more desirable in a daily driven car, and sacrificing five to six peak horsepower for the same amount in the midrange will make the power more useable. In looking at flow capacities of the two diameters in a dual-exhaust configuration, the transition point where the benefit of a 3-inch versus 2.5- inch exhaust start to drift apart is near the 400-450hp mark. At this point, the horsepower and torque variations become more substantial, and the loss and gain needs to be more carefully analyzed."
MagnaFlow's straight-through...
MagnaFlow's straight-through design silences without causing a bottleneck. "Our mufflers consist of a perforated core pattern wrapped in stainless steel wool for maximum longevity," says Richard.
Since our initial goal is to get the Fairlane into the 11s, we decided a three-inch system would work better with our single-plane Victor Jr. intake. We also asked Richard about the need to run an X-pipe. "The X-pipe is an integral part of our design. The X-pipe has been around for a long time; however, many people only know it as something NASCAR uses or as a 'crossover' pipe. The X-pipe, or as we call it, the TRU-X, increases the efficiency of the exhaust system using scavenging. Scavenging is a means of using existing exhaust pulse energy to enhance total flow. To maximize the output of our TRU-X, it should be placed where it can utilize the high-speed gasses expelled from the engine at a point where the vacuum charge created as the exhaust pulse crosses the X can create a pressure drop to a bank of cylinders or individual cylinder in its exhaust stroke. The engine can more efficiently expel spent exhaust gasses, making for greater cylinder filling, which equates to more power."
With a plan in place, we trailered the Fairlane over to MagnaFlow's R&D center so they could tame the raucous sound from our 408 and help us get another step closer to hitting the track.
Chassis-Dyno Throwdown
We started out with a 408 stroker that put out 552 hp and 530 lb-ft of torque on the Superflow engine dyno at Westech. Then we got curious how much of that the exhaust and drivetrain ate up, so we took it back to Westech for a run on the Superflow chassis dyno. Even though the 408 was perfectly tuned on the engine dyno, it needed a bit of tweaking in the car since it was running a bit fat at cruise. We swapped out the 73/73 jets in our Holley 950HP carb for a 76/70 combo, and we were rewarded with a best pull of 448 rear-wheel hp and 404 lb-ft of torque. It's reassuring to have the engine dyno numbers backed up on the chassis dyno. We attribute the loss of only 104 horsepower to the free-flowing FPA headers and three-inch MagnaFlow exhaust. Will e get into the 11s? According to our math, we ave a shot atit. Now where's that Chevelle?
 This is what puts the "flow"...  This is what puts the "flow" in MagnaFlow Their straight-through design doesn't restrict exhaust gasses. We asked Richard to explain this. "Our design was developed based upon the need for a highperformance muffler that could manage day-to-day use while providing adequate noise control and flow capacity. |  Included with our FPA headers...  Included with our FPA headers were the mating sides of the collectors. Since our system is stainless, we didn't use the flared pipe, but we did use the two-bolt connector since it's nickel-coated. |  You should also levels when...  You should also levels when choosing 3- and 2.5-inch exhaust. explained, "The two exhaust at different the sound varies. more controlled the 2.5-inch will better. The 3-inch will lower frequency, absorb as much Where horsepower primary concern, is chosen for its sound alone, and who can blame them? |
 Back in the day, H-pipes were...  Back in the day, H-pipes were the rage. The only problem is that fast-moving exhaust isn't good at making 90-degree turns. The X-pipe, however, is far more efficient at doing this. In both cases there's a scavenging effect, but the X-pipe also has great pressure balance. |  Here's how the collector of...  Here's how the collector of the FPA headers lined up with the Fairlane's transcrossmember. It's offset to the side, but is close enough to work. This also shows the sweet two-bolt ball flange that comes with the FPA headers. |  MagnaFlow routed the threeinch...  MagnaFlow routed the threeinch the C4 crossmember. maximum ground clearance. to fit was the most of the install. |
 When assembly starts, a pole...  When assembly starts, a pole jack or other support is mandatory. You could also try bribing a few buddies with pizza and beer. |  The 14-inch polished stainless...  The 14-inch polished stainless mufflers (PN 14329, $95.95 each) are attached to a reinforced spot on the bottom of the Fairlane with stainless hangers. Choosing the right-sized muffler isn't easy. According to Richard, "Inlet and outlet configuration are looked at as the most important feature for fitment; however, they also contribute to how a muffler will control noise. |  Next up, MagnaFlow installed...  Next up, MagnaFlow installed the over- axle pipe. Guys on a tight budget sometimes dump the exhaust right after the muffler, but that will result in more cabin noise and the possibility of toxic fumes wafting to the passenger compartment. |
 |  Lastly, MagnaFlow installed...  Lastly, MagnaFlow installed the tailpipe sections. The end is supported by a bracket to the frame. Also note the use of band clamps throughout the installation. At first, we were going to build the system from coated steel, but MagnaFlow convinced us to go with stainless. | |